1. Field of the Invention
This invention relates to a loudspeaker system having a speaker enclosed in a cabinet, and more particularly to such enclosed loudspeaker systems which are provided with a heat pipe for removing heat from the voice coil of the loudspeaker.
2. Description of the Prior Art
Generally, the maximum drive current which can be tolerated by a loudspeaker is substantially determined by the ability of the voice coil to withstand elevated temperatures. Therefore, for the purposes of dissipating unwanted heat from the voice coil, it has been proposed to blacken, as with paint, the magnetic circuit elements of the speaker, especially in the portion thereof near the air gap in which the voice coil is positioned, so that heat developed in the voice coil by the drive current is radiated across the air gap and then dissipated by way of the magnetic circuit elements. However, the foregoing heat dissipation does not sufficiently remove the heat from the voice coil to permit high drive currents to be applied to the voice coil for a substantial length of time.
Accordingly, in order to radiate the heat effectively, it has been proposed that a heat pipe be provided for removing heat from the speaker drive means. In one such proposed loudspeaker, one end portion of a heat pipe is in thermal contact with the drive means for the speaker and the other end portion of the heat pipe is provided with a plurality of fins for dissipating heat generated by the drive current. Although an enclosed loudspeaker system which incorporates a heat pipe, as aforesaid, does increase the tolerable input current, such increase in the allowable current is limited as the finned portion of the heat pipe is entirely within the speaker enclosure. Thus, as long as there is no provision for removing heat to the exterior of the enclosure, the temperature at the inside of the enclosure will rise, and as a result of the elevated temperature inside the enclosure, the heat pipe can not cool the drive means efficiently.